Abstract:
<p>Both dynamic conformal arc therapy (DCAT) and three-dimensional conformal radiation therapy (3D-CRT) are well-established techniques and have commonly been used for stereotactic radiosurgery (SRS) treatment in brain metastases. However, for multiple metastases, a much longer treatment time results from multi-isocenter setup in DCAT and 3D-CRT. The aim of this study is to investigate the treatment of multiple brain metastases using single-isocenter volumetric modulated arc therapy (VMAT) compared with conventional multi-isocenter DCAT and 3D-CRT.</p><p>A series of 17 patients with 2 to 5 brain metastatic lesions were studied. For patients treated with DCAT/3D-CRT plans, VMAT plans were retrospectively generated, and vice versa. The number of isocenters was proportional to the number of PTVs in DCAT/3D-CRT plans while single-isocenter was employed in VMAT plans. The DCAT/3D-CRT and VMAT plans were generated using BrainLAB iPlan® RT Dose v4.1.1 and Varian Eclipse® v8.6 treatment planning system, respectively. All plans were designed to be delivered on Novalis Tx® system.</p><p>Conformity for VMAT plans was equivalent to or better than that for DCAT/3D-CRT plans. VMAT and DCAT/3D-CRT plans have similar target coverage, and VMAT plans have higher quality of coverage. However, the mean increase of 46% in the volume of low-dose region receiving 5 Gy was observed in VMAT plans. In addition, the distance between individual PTVs and VMAT isocenter has no impact on VMAT plans. The mean monitor units (MU) decreased by 42% and the mean treatment time decreased by 49% for VMAT plans.</p><p>This work suggests that single-isocenter VMAT is promising for SRS in the treatment of multiple brain metastases. Single-isocenter VMAT is able to achieve comparable dose conformity, target coverage, and quality of coverage to conventional DCAT and 3D-CRT plans with significantly superior delivery efficiency. However, single-isocenter VMAT might result in a larger low-dose region.</p>
